The present invention relates to sprinklers used in automatic fire extinguisher systems for buildings and the like, and in particular, relates to a fast response sprinkler head and fire sprinkler system for use in environments wherein one or more obstructions are positioned in proximity to the sprinkler head.
Automatic sprinklers have long been used in automatic fire extinguishing systems for buildings in order to disburse a fluid to control a fire. Typically, the fluid utilized in such systems is water, although systems have also been developed to disburse foam and other materials. Historically, sprinkler heads include a solid metal base connected to a pressurized supply of water, and some type of deflector used to alter the trajectory of the water flow. Alteration of the water flow by the deflector generates a defined spray distribution pattern over the protected area. The deflector is typically spaced from the outlet of the base by a frame, and a fusible trigger assembly secures a seal over the central orifice. When the temperature surrounding the sprinkler head is elevated to a pre-selected value indicative of a fire, the fusible trigger assembly releases the seal and water flow is initiated through the sprinkler head.
Fire extinguishing sprinkler heads come in three general structural types, namely, upright, pendent and sidewall. Of interest to the present application are the pendent type and, in particular, upright structural type. Pendent sprinklers depend below a fire extinguishing fluid supply pipe, such as a water pipe. In pendent sprinklers, when the fusible trigger assembly reaches a pre-selected temperature due to the presence of fire, the fusible trigger assembly releases the seal positioned over the outlet, enabling water to flow through the central orifice of the sprinkler head in a downward direction. As the water exits from the sprinkler head, it is typically disbursed by the deflector which alters the trajectory of the water so as to define a spray distribution pattern in an attempt to control the fire.
An upright sprinkler differs from a pendent sprinkler in that it projects upwardly from the fluid supply pipe. When an upright sprinkler is activated, the water flows upward through the sprinkler head and is expelled from the central orifice in an upward direction. Gravitational forces, in combination with the deflector spaced a pre-selected distance above the central orifice, results in the formation of a downwardly moving spray distribution pattern in an attempt to control a fire. In addition to some common benefits and advantages, pendent and upright sprinklers each have some benefits relative to the other type. Upright sprinklers for example, have less of a tendency to collect contaminant build-up since the containments settle down into the branch pipe and thus potential blockage is reduced.
Historically, automatic sprinkler systems have been designed to achieve what is referred to as “fire control” about a protected area. In the fire control method of combating fires, the automatic sprinkler system is designed and installed such that a relatively large number of individual sprinklers will activate upon detection of a fire. That is, in response to a fire, not only will the sprinklers closest to the fire be actuated, but also sprinklers which protect the areas surrounding the fire, so as to define a controlled area. While it is anticipated that the sprinklers immediately above the fire may not be able to extinguish the fire, the goal of the fire control method is to actuate the sprinklers about the fire to pre-wet the combustible materials in the fire's general vicinity to prohibit the fire's growth. Thus, the fire control method seeks to confine the fire within a predetermined area until additional fire fighting methods are deployed, such as response by a fire department, in order to extinguish the fire.
Beginning in the 1970's, industries began more widely using relatively large warehouses for the storage of product. To effectively utilize space within these warehouses, product is normally stacked on pallets or racks in a vertical arrangement. These warehouses may reach approximately 30 feet in height and contain stacked pallets as high as approximately 25 feet. Traditional sprinklers, designed and installed so as to provide “fire control,” have proven ineffective in combating fires ignited in these large warehouses. As the vertically stacked pallets may exceed over twenty feet in height, fires ignited within these pallets produce a plume of combustion gasses which rapidly travels upward and subsequently impacts the ceiling of the warehouse. The rapid generation of these combustion gases creates a zone of high temperature above the fire, and thus when the sprinkler head is activated, an unacceptable quantity of water expelled from the sprinkler is evaporated within this high temperature zone before it reaches the site of the fire. As a result, less water is actually delivered to the fire and hence prevents effective fire control.
After impacting the ceiling, these combustion gases span out in a horizontal direction along the surface of the ceiling. The rapid movement of the combustion gases along the ceiling results in the actuation of a large number of sprinkler heads located a remote distance from the perimeter of the fire. The mass actuation of sprinkler heads within the warehouse produces several unacceptable consequences. First, the near simultaneous actuation of a large number of sprinkler heads produces a significant decrease in the water pressure delivered to each individual sprinkler head. Consequently, less water is available for delivery to the fire and thereby provides an opportunity for the fire to spread. Furthermore, actuation of remotely located sprinkler heads results in water damage to the product protected by such sprinklers.
In response to the inadequacies of existing sprinkler heads and the “fire control” deployment method, the sprinkler industry began the design and installation of “Early Suppression Fast Response” (hereinafter referred to as “ESFR”) sprinkler heads. As the name indicates, the theory behind ESFR is to deliver a sufficient quantity of water during the early stages of fire development in order to suppress and extinguish the fire and deny the opportunity for fire growth. In order to achieve the goal of early suppression, ESFR sprinklers must quickly generate a sufficient quantity of water capable of penetrating the fire plume and thus be delivered to the core of the fire, often referred to in the industry as the “fuel package.” To deliver a sufficient quantity of water to the “fuel package”, ESFR sprinklers are equipped with a thermally sensitive fusible trigger assembly capable of actuating the sprinkler head shortly after ignition of the fuel package. Normally, ESFR sprinklers utilize fusible trigger assemblies which have a fusing temperature between approximately 155° F. and 175° F.
To determine the ability of these ESFR sprinklers to suppress high challenge fires generated by industrial warehouses, the sprinkler industry, and in particular the Factory Mutual Research Corporation (hereinafter “FMRC”), developed the concepts of actual delivered density (hereinafter “ADD”), required delivered density (hereinafter “RDD”), and response time index (hereinafter “RTI”) as quantifiable measures of sprinkler performance. The RDD is the amount of water that must be delivered to a fuel package composed of a particular type of combustible material in order to achieve suppression. The establishment of a RDD value for a particular fuel package is achieved by various tests most oftenly conducted by the FMRC. The ADD value depends on the construction of the particular sprinkler head and is defined as the amount of water which is actually deposited onto the top of a combustible fuel package. Generally speaking, the RDD value increases as a function of time once ignition of the fuel package is initiated. During the maturation of the fire, the RDD increases as a function of time because as the fire develops, more combustion gases are generated and thus more water must be generated due to the quantity of water evaporated by the fire plume. The ADD generally decreases as a function of time, until the fire reaches full maturation. The decrease in the ADD as a function of time is also due to the growth of the fire plume, which results in an increasing water evaporation rate, and thus reduces the quantity of water actually delivered to the fuel package. Under the ESFR theory, early suppression is achieved if the ADD is greater than the RDD.
The ADD value of a particular sprinkler is largely a function of the discharge coefficient or “K” value. The K value is defined by the following equation:k=q/√{square root over (p)}                q=flow in gallons per minute; and        p=water pressure pounds per square inch.As a result of testing by the sprinkler industry, ESFR sprinklers must have a K value of at least 13.5, and preferably 14 or greater.        
The RTI value is essentially a measure of the thermal sensitivity of the fusible trigger assembly which actuates the sprinkler head. Consequently, the lower the RTI value of a particular sprinkler, the faster the actuation time of the sprinkler head in response to a fire, which in turn decreases the ADD value necessary to extinguish the fire.
Since the advent of ESFR sprinklers in the 1970's, the sprinkler industry has attempted to design upright sprinklers having the ADD values necessary to adequately suppress a fire. Despite these attempts, heretofore, the industry has been unable to generate an upright sprinkler head capable of achieving ESFR standards, and has only produced pendent sprinklers having the requisite ADD criteria. The inability of the industry to generate an ESFR sprinkler having an upright design has presented problems in the industry, specifically, in the retrofitting of warehouses. Prior to the advent of ESFR sprinklers, many warehouses employed traditional upright sprinkler assemblies. Consequently, retrofitting warehouses designed to accommodate upright sprinklers with ESFR pendent sprinklers has required warehouse owners to tear out existing piping and replace the same with piping capable of supporting pendent ESFR sprinklers. This, in turn, has increased the cost and complexity of installing an ESFR sprinkler system.
In order to provide uniformity in the design and installation of sprinkler systems, as well as to maximize the probability that the installed sprinkler system will operate in an effective manner, the National Fire Protection Association (hereinafter referred to as the “NFPA”) generates criteria or regulations for both the design and installation of fire sprinkler systems. The NFPA is comprised of a wide cross-section of companies and organizations having expertise and interest in fire protection safety. The first set of regulations issued by the NFPA occurred at the beginning of the 20th Century and has been continuously updated in light of advances and changes in technology. The NFPA regulations or guidelines are based on data gained by over one hundred years of experience in the evaluation of sprinkler systems. Compliance with NFPA guidelines, in particular NFPA 13, which governs the installation of sprinkler systems (discussed hereinafter in detail), is frequently required by federal and state enforcement agencies, and is accepted by the insurance industry as the definitive guideline concerning the installation and design of sprinkler systems. Consequently, as a commercial practicality, sprinkler designs and the installation of sprinkler systems must be able to perform successfully within the guidelines set by the NFPA, and in particular NFPA 13. Failure to conform or operate successfully within the NFPA guidelines effectively prohibits the commercial viability of a particular sprinkler design or its installation.
In addition to providing guidelines concerning the design and installation of sprinklers, the FMRC, in conjunction with the NFPA, have established “commodity” classifications which categorizes materials commonly found in warehouses or storage facilities. Each commodity classification segregates materials according to their degree of combustibility and the operating requirements necessary to extinguish them. For each of these commodities, a particular sprinkler head must meet certain water supply and discharge requirements in order to provide adequate protection. Currently, materials are classified in the following commodity classifications: class 1 through 4, carton unexpanded plastic, cartoned expanded plastic, uncartoned unexpanded plastic and uncartoned expanded plastic. Of these commodities, uncartoned unexpanded and expanded plastic commodities represent the two most challenging fire hazards, with uncartoned expanded plastic carton commodities representing the most challenging fire scenario.
Of particular importance to the present invention are those sections of NFPA 13 which govern the installation of ESFR sprinklers in areas having obstructions supported by and depending from, or otherwise supported below, the ceiling of a warehouse or enclosure. The 1996 Edition of NFPA 13 provides specific spatial requirements concerning the placement of ESFR sprinklers in proximity to obstructions that prevent the sprinkler from developing an effective spray distribution pattern. Specifically, §4-11.5.2 is directed to the issue of obstruction to sprinkler discharge in ESFR sprinklers, and defines a minimum horizontal or lateral distance that the sprinkler head must be placed from the obstruction. NFPA 13 (1996 ed.), §4-11.5.2 states as follows:                Sprinklers shall be positioned such that they are located at a distance three times greater than the maximum dimension of an obstruction up to a maximum of 24 inches (609 mm) (e.g. structural members pipes, columns, and fixtures). Sprinklers shall be positioned in accordance with Figure 4-11.5.2 where obstructions are present.        
Figure 4-11.5.2, referenced in §4-11.5.2 of NFPA 13 (1996 ed.) is reproduced herein as FIG. 1. In FIG. 1, “a” corresponds to the horizontal or lateral distance between the sprinkler head and the obstruction, whereas “c” defines the height and “d” the width of the obstruction positioned below the sprinkler head. An “obstruction” as used in §4-11.5.2 may be a bottom chord of a truss or joist, a pipe, duct, light fixture, or similar horizontally positioned fixture commonly encountered in a warehouse or storage facility.
The 1999 edition of NFPA 13 § 5-11.5.1 details the requirements of ESFR sprinklers when obstructions are present at or near the ceiling and states as follows:                Sprinklers shall be arranged to comply with Table 5-11.5.1 and Figure. 5-11.5.1 for obstructions at the ceiling such as beams, ducts, lights, and top cords of trusses and bar joists.        
Table 5-11.5.1 and FIG. 5-11.5.1 are reproduced herein as FIGS. 17 and 18, respectively. In addition, the 1999 version of NFPA 13, in § 5-11.5.2, addresses the placement of ESFR sprinklers when isolated obstructions are present below the elevation of sprinklers and requires that:                Sprinklers shall be installed below isolated noncontinuous obstructions that restrict only one sprinkler and are located below the elevation of sprinklers, such as light fixtures and unit heaters.        
Furthermore, § 5-11.5.3 of NFPA 13 (1999 ed.) provides guidelines concerning continuous obstructions located below the ESFR sprinklers of a sprinkler system and provides:                Sprinklers shall be arranged to comply with Table 5-11.5.1 for horizontal obstructions entirely below the elevation of sprinklers that restrict sprinkler discharge pattern for two or more adjacent sprinklers, such as ducts, lights, pipes, and conveyors.        
Finally, § 5-11.5.3.2 of an NFPA 13 (1999 ed.) requires:                ESFR sprinklers shall positioned a minimum of one foot (0.3 m) horizontally from the nearest edge to any bottom cord of a bar joist or open truss.        
Thus, it can be seen from the above cited sections of both the 1996 and 1999 edition of NFPA 13 that various guidelines and regulations govern the installation of ESFR sprinklers in applications where the area to be protected includes one or more types of obstructions. It is believed that the sections cited above from NFPA 13 (1999 ed.) define and clarify additional guidelines concerning the installation of ESFR sprinkler systems, and acts as a supplement to § 4-11.5.2 of NFPA 13 (1996 ed.).
Conformance with the above cited sections of NFPA 13, has heretofore been a practical necessity governing the installation of all ESFR sprinkler assemblies due to the inability of sprinkler manufacturers to produce an ESFR sprinkler head having the requisite ADD value for a fuel package consisting of a particular type of combustible material, which is also capable of developing a spray distribution pattern in proximity to these obstructions. Conformance with NFPA 13 (1996 ed.) §4-11.5.2, and the above-referenced sections of NFPA 13 (1999 ed.) has added additional cost to the installation of sprinkler systems by requiring the placement of additional sprinklers in areas surrounding the obstruction. Furthermore, the various sections of NFPA 13 (1999 ed.) has increased the complexity of the installation procedure of ESFR sprinklers in areas wherein obstructions are present. In addition, as a conventionally sized warehouse or storage facility may contain many different types of obstructions, the installation of sprinkler systems in these facilities is often a complex procedure. Moreover, in certain circumstances, adherence to NFPA 13 (1996 ed.) §4-11.5.2, and the various sections of NFPA 13 (1999 ed.) has resulted in particular areas receiving only a marginal quantity of water and thus, are particularly vulnerable to the generation and growth of a fire. That is, in order to satisfy the above cited sections of NFPA 13, it is often necessary to place a sprinkler head on both sides of the obstruction. Consequently, when the site of ignition is directly, or approximately directly, under the obstruction, only the outer periphery of the spray distribution pattern of both the sprinkler heads reach the conflagration. As a result, fires generated proximate to these obstructions have an increased opportunity to grow and spread to adjoining areas given the often marginal protection afforded by the pair of sprinkler heads.
Consequently, there exists a need for a fast response, upright sprinkler which can effectively provide a spray distribution pattern when used in proximity to obstructions and can provide the necessary ADD values required to suppress or extinguish a fire.